Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
According to Forte, Schoenberg developed the pentadcanonically in "Farben" (also titled "Summer Morning by a Lake" or "Chord-Colors"), while Alban Berg used the chord as one of three on which Act I scene 2 of Wozzeck is based. The pentad is "almost octatonic" and has been called "a 'classic' atonalset type". The chord relates the movement to the other movements of the piece, with it appearing as the first chord of movement No.2 and in movement No.4, "The figure in the first bar is actually a horizontal version of the chord from the preceding movement."
References
Elizabeth L. Keathley, "Schoenberg's Op. 16/IV: An Examination of the Sketches", Theory and Practice Vol. 17 (1992): pp.67–84, citation on p.80.
Michiel Schuijer, Analyzing Atonal Music: Pitch-Class Set Theory and Its Contexts (Eastman Studies in Music 60), Rochester: University of Rochester Press, 2008, p.109. ISBN978-1-58046-270-9.
^ Allen Forte, "The Golden Thread: Octatonic Music in Webern's Early Songs, with Certain Historical Reflections", in Webern Studies, edited by Kathryn Bailey, pp.74–110. New York: Cambridge University Press, 1996, p.98n21. ISBN0-521-47526-0.
Allen Forte, The Structure of Atonal Music, New Haven and London: Yale University Press, 1973, pp.55,84,112,166&180.
^ Allen Forte, "The Golden Thread: Octatonic Music in Webern's Early Songs, with Certain Historical Reflections", in Webern Studies, edited by Kathryn Bailey, pp.74–110. New York: Cambridge University Press, 1996, p.98. ISBN0-521-47526-0.
Elizabeth L. Keathley, "Schoenberg's Op. 16/IV: An Examination of the Sketches", Theory and Practice Vol. 17 (1992): pp.67–84, citations on pp.77&80.